Stop mechanism for presses



NOV. 1, 1938.. sMlTH 2,134,933

STOP MECHANISM FOR PRESSES Filed Aug. 20, 1937 2 Sheets-Sheet 1 G gFig.2. 5 65 "QC 61 v Dixon H3177/fh 727W ,L@%

NOV. 1, 1938. $M|TH 2,134,933

STOP MECHANISM FOR PRESSES Filed Aug. 20, 1937 2 Sheets-Sheet 2 927M,,Gia

I @UCMMM S Patented Nov. '1, 1938 UNITED STATES PATENT OFFICE STOPMECHANISM FOR PRESSES Application August 20, 1937, Serial No. 160,180

6 Claims.

The invention relates generally to presses, or more particularly topresses of the deep drawing type, and primarily seeks to provide a novelsafety stop mechanism adapted to automatically stop the press whenever ajamming of parts is likely to occur.

In a press of the character stated, there is provided .a reciprocablecrosshead, a die block carried by the'crosshead, and a draw ring onwhich a blank to be drawn and shaped is supported and into which saidblank is pressed by the block in opposition to a knockout pad whichbecomes effective upon recession of the block to knock out the drawn endunit or strip it from said ring. Occasionally, in drawing a one piececan or cover, excessive friction set up by the drawn sides of the formedunit against the draw ring causes the pad to stick and fail to ejectsaid formed unit. Obviously, when such a jamming of parts occurs, shouldanother blank be fed into the press and the press continue in itsoperation, great damage is likely to be the result. My invention seeksto avoid this condition;

In its more detailed nature, the invention resides in the provision of apair of electrical make and break contact devices or switches connectedin series with a power cut oil means for discontinuing a press motionlikely to cause damage following a jamming of the pad, and respectivelyassociated with the crosshead and the pad whereby one switch is closedwhen the crosshead is raised and the other when the pad is lowered, thecircuit through said switches being completed only when the pad remainsabnormally lowered when the crosshead is raised.

With these and other objects in view which will hereinafter appear, thenature of the invention will be more clearly understood by following thedescription, the appended claims,v and the several views illustrated inthe accompanying drawings.

In the drawings,

Figure 1 is a somewhat diagrammatic front elevation and part verticalsection illustrating a press embodying the invention.

Figure 2 is an enlarged detail face view of the crosshead actuatedswitch unit.

Figure 3 is an enlarged fragmentary detail vertical section illustratingthe pad actuated switch unit.

Figure 4 is a diagrammatic view illustrating the positions of the switchunits when the crosshead and pad are elevated.

Figure 5 is a view similar to Figure 4 illustrating the positions of theswitch units when the crosshead and the pad are lowered.

Figure 6 is a view similar to Figure 4 illustrating the positions of theswitch units when the crosshead is elevated and the pad is stuck in itslowered position.

In the drawings in which like numerals of 5 reference indicate likeparts in all of the figures,

I have illustrated the invention applied to a conventional form of pressincluding a base frame 5 having the usual table or bed 6, and asuperstructure I in which the crank shaft 8 has rota- 10 tive bearing.The crank shaft is driven by power transmitting connections 9 from amotor l0 and is connected by pitmen II with a crosshead l2 reciprocablyguided in the superstructure l. The crosshead I2 carries the usual dieblock equip- 15 ment including the plunger i3 and the blank cutting andholding ring l4.

Upon the bed 6 is mounted the usual blank cutting ring Hi, the draw ringl6, and the knockout pad H. The pad I1 is carried by a plunger or 20stem 18 vertically slidable in a bearing l9 and held in its raisedposition, shown in Figure 1, by a spring equipment 20.

The stem I8 is provided with a recessed portion 2| and a flattenedswitch closing face 22. 25 See Figures 1 and 2.

Power input lines are diagrammatically indicated at 23 and these linesare connected by wires 24 and 25 with the motor ID. A cut out switch 26is connected in either of the lines supplying 30 current to the motor,and it will be obvious that whenever this switch is open, and the motorcircuit thus broken, operation of the motor and of the press as a wholewill be discontinued. While I have illustrated the invention arranged 35to discontinue motor operation, it is to be understood that my improvedautomatic stop control devices are applicable to control the operationof any means movable to perform a function incident to operation of thepress, for example, a 40 blank feeding means.

In the practical development of my invention,

I provide a switch unit which is pad-actuated, and a switch unit whichis crosshead-actuated, the former being closed each time the pad is 45pressed inwardly or lowered, and the latter being closed each time thecrosshead is raised.

The pad-actuated switch unit includes a plunger 21 reciprocablehorizontally in and through a bore 28 formed in the bed 6, the in- 50wardly extended end of said plunger extending into the recess 2| withwhich the pad stem I8 is provided. An abutment head 29 is carried by theplunger 21 and engages the bed wall in a counterbore 30 to determine theposition of the I plunger end in the pad stem recess 2|. The counterboreis internally threaded to receive an insulating bushing 3| having a bore32 to slidably receive another contact plunger 33 having an abutmenthead 34 disposed in a counterbore 35 in said bushing. An insulatingwasher 36 closes the open end of the counterbore 35 and forms a switchchamber therein. The outer end of the contact plunger 21 projectsthrough the washer into the switch chamber where it is equipped with abreaker point 31'opposed to a similar breaker point 35 carried by theplunger 33. At its outer, exposed end the plunger 33 carries an abutmenthead 39 and circuit wiring connecting nuts 40. A spring 4| yieldablyholds the plunger 33 opposed to the plunger 21, the head 39 determiningthe normal position of said plunger, and a spring 42 holds the abutmenthead 29 against the bed wall to position the contact member 21 in thepad stem seat as previously described. The breaker points 31 and 33 areseparated whenever the pad is in the raised posiiton shown in Figure l,and will be brought into circuit making engagement each time the pad isdepressed.

The crosshead-actuated switch unit equipment includes an actuating cammember 43 adjustably secured as at 44 to the crosshead so as to bemovable therewith. A mounting plate 45 is accured to the press framesuperstructure 1 adiacent the path of travel of the crosshead cam member43 as shown in Figure 1. On said plate there is affixed a contact block45, of insulating material, which carries a contact member 41 yieldablysupported therein as at 45 and equipped with an abutment head 49determining the position thereof, and circuit wiring connecting means50. Another contact block 5|, of insulating material, is secured uponone arm of a bell crank lever 52 which is pivotally mounted on the plate45 as at 53. The other arm of the bell crank carries a roller 54 whichis engaged by the crosshead cam member 43 to move the block 5| towardthe block 45 each time the crosshead is elevated. A spring 55, connectedto the plate 45 and to an arm of the bell crank, tends to move the block5| away from the block 45. The block 5| carries a contact member 55,having provision at 51 for connection with suitable circuit wiring, anda breaker point 55 engageable with a similar breaker point 55 carried bythe contact member 41. See Figure 2.

Suitable circuit wiring 50 connects the switch units in series with thepower lines 23 through a solenoid 5|. The circuit wiring may includeframe ground connections 52 if desired, and it will be noted that thepad stem l8, engageable by the contact plunger 21, is included in thecircuit connections. See Figures 1 and 4 to 6. A make and break member53 is movable with the core of the solenoid 5| which is positioned sothat each time the solenoid winding is energized the core will be movedto break the motor circuit across the switch 25 as shown in Figure 6.

In Figures 4 and 5 of the drawings, positions of normal operation of thepress are shown. In Figure 4 the crosshead is elevated and itsassociated switch unit 45, 5| is in the closed position. The pad iselevated and its associated switch unit 21, 33 is in the open, circuitbreaking position. The motor circuit is closed across the switch 25.

In Figure 5, the crosshead is lowered and its associated switch unit 45,5| is in the open, circuit breaking position. The pad is depressed orlowered and its associated switch unit 21, 33 is in the closed posiiton.The motor circuit is closed across the switch 26.

Thus it will be seen that during all normal functions of the press thesolenoid energizing or power cut oil controlling circuit 50 will bebroken by one or the other of the two switch units 45, 5|, or 21, 33 asshown in Figures 4 and 5.

It sometimes happens that a formed article will jam in the press due toexcessive frictional engagement in the draw ring I5, and the pad willstick in its depressed or lowered position. Obviously, if more blanksare fed to the press and the press is allowed to continue in operation,serious damage will be the result. Under these conditions my improvedstop control becomes effective to prevent damage by cutting off thesupply of electrical energy as illustrated in Figure 6.

In Figure 6, I have diagrammatically illustrated what happens when thepad |1 jams or sticks in its depressed position. It will be recalledthat in this position of the pad the associated switch unit 21, 33 isclosed. As the crosshead rises following the stroke which jammed thepress and caused the pad to stick, it will close its associated switchunit 45, 5|, as shown in Figure 6, and with both switch units closed,the circuit 5|] is completed and the solenoid 6| will be energized andthe member 53 moved to break the power circuit 24, 25. cuit breakingoperation can take place only during an abnormal, jammed condition ofthe press when the pad l1 sticks in its depressed position, holding itsassociated switch unit closed, and the crosshead rises to its elevatedposition, closing its associated switch unit, thus completing the powercut off controlling circuit 55 through both switch units.

I claim:

1. In a press, the combination of a reciprocable crosshead, a formingdie carried. by said crosshead, forming means engageable by said die andincluding a knockout pad movable inwardly with the die during theforming operation and retumable upon withdrawal of the die to eject theformed article, and means effective upon sticking oi said pad to stopoperation of the press, said last named means including a switch movableto a circuit closing position when the pad is in its inwardly movedposition and a switch movable to a circuit closing position when saidcross head is in a die retracted position.

2. In a press, the combination of a reciprocable crosshead, a formingdie carried by said crosshead, forming means engageable by said die andincluding a knockout pad movable inwardly with the die during theforming operation and returnable upon withdrawal of the die to eject theformed article, and means effective upon sticking of said pad to stopoperation of the press, said last named means including a pair ofswitches connected in series in a power stop control circuit one saidswitch being movable to a circuit closing position when the pad is inits inwardly moved position and the other said switch being movable to acircuit closing position when said crosshead is in a die retractedposition.

3. In a press, a crosshead movable between projected and retractedpositions, a forming die carried by said crosshead, forming devicesengageable by said die and including a knockout pad movable inwardlywith the die and returnable upon retraction of said die to eject theThis power cir-' means and including control devices effective only whenan inward position of the pad coincides with a retracted condition ofsaid crosshead.

4. In a press, a crosshead movable between projected and retractedpositions, a forming die carried by said crosshead, forming devicesengageable by said die and including a knockout pad movable inwardlywith the die and returnable upon retraction 0;? said die to eject theformed article, means for imparting motion to the press, a controlcircuit for disabling said means and including a pair of switchesrespectively actuated by movement of said pad and crosshead andcooperatively efiective only when an inward position of said padcoincides with a retracted condition of said crosshead.

5. In a press, the combination of two elements reciprocable incident toa pressing operation, power applying means for imparting movement to atleast one said element, and control means for said power applying meansincluding two devices actuated by movement of said elements andcollectively eflfective to discontinue operation of the power applyingmeans, said devices being actuated alternately during normal movement ofsaid elements and collectively only when one said element sticksabnormally at its device actuating position whereby power will be cutoil whenever such sticking occurs.

6. In a press, the combination of two elements reciprocable incident toa pressing operation,

power applying means for imparting movement to at least one saidelement, and control means for said power applying means including anelectrical control circuit and two control switches connected in seriesin said circuit, and means actuated by movement of said elements foropening one switch and closing the other at each stroke of reciprocationof the elements whereby upon sticking or one element both switches willbe closed to energize said control circuit.

DIXON HINSHAW 3mm

